1. Field of the Application
The present application relates to an axial turbomachine compressor drum, more particularly with a rotor stage of such a compressor, knowing that the drum can be composed of an assembly of several parts corresponding to different rotor stages; and more particularly still, with construction measurements of an axial turbomachine compressor drum, these measurements being intended in particular to reduce the drum.
2. Description of Related Art
In general, a compressor drum is a generally symmetrical hollow body in revolution in relation to its axis of rotation, which corresponds to the axis of the turbomachine. The hollow body has a general oval or ogive shape according to the form of the flow. Several rows of vanes are fixed on the drum so as to form different rotor stages, knowing that each rotor stage cooperates with a stator stage composed of a row of stator vanes, each pair of rotor and stator stages thus forming a compression stage of the compressor.
The centrifugal stresses exerted by the rotor vanes on the drum are very high, in particular when the drum is of large diameter and/or of high rotation speed. It is a constant worry for the designers of compressors to ensure a satisfactory mechanical resistance of the drum and vanes while taking care to reduce the drum to the maximum.
A traditional design is notably revealed in U.S. Pat. No. 4,784,572. The drum is composed of a generally smooth veil, except for the sealing elements intended to cooperate with the abradable material of the stator ferrules. It is equipped with reinforcements on its interior face on the level of the rotor vanes. These reinforcements form an integral part of the drum and are in the form of internal ribs of which the thickness is greater on the level of their ends directed towards the interior of the drum. These reinforcements are commonly called “leeks” because of their form. These reinforcements appreciably weigh down the drum because of their massiveness. The latter is the result of an optimum between two tendencies, namely, that of adding material in order to increase the stiffness of the drum and that of limiting the addition of material on the drum because of the centrifugal forces and knowing that this addition of material is all the more penalizing as the material is farther away from the axis of rotation. The rotor vanes are equipped with a series of circular ribs intended to be diffusion welded on the exterior surface of the veil of the drum. These ribs share in the stiffness of the drum. They also make it possible to level the rotor vanes with the stator vanes. The construction proposed in this document is interesting from a point of view of stiffness but imposes, however, a significant massiveness which is penalizing notably for the weight of the compressor in itself.
Patent document WBC 2-059-819 A reveals a compressor drum and tries to propose a reduced drum construction. The drum consists primarily of a series of sections assembled by diffusion. The drum comprises a veil equipped with internal ribs on the right of the sites of the veil intended to receive the rotor vanes. The veil comprises on its exterior surface a pair of ribs with each section intended to receive a row of vanes. This pair of ribs forms a U-section receptacle intended to receive the root of a vane especially designed to cooperate with this receptacle. Fixing is done by insertion of a pin or stitches through the U-shaped wings and the wings of the vane root. This construction certainly provides a favorable rigidity, but it imposes certain geometrical tolerances on the level of the jointing of the vane root and the receptacle as well as a significant mass, notably because of the ribs and the connection pin.
European Patent Application No. 08172923.0, filed by the filer of this application, reveals a reduced compressor drum comprising, in addition to the veil, a series of sections intended to receive, each, a row of rotor vanes, these sections being elevated in relation to the veil. The exterior surface of these sections delimiting the fluid stream is equipped with a series of openings, each of these holes being intended to receive a vane platform. The platform is then welded to the wall. These holes extend longitudinally on nearly the totality of the surface delimiting the aerodynamic fluid stream. These holes bored in the wall section are unfavourable, because they partially weaken it.
Although great strides have been made in the area of axial compressors, many shortcomings remain.